Lightning arrester



July 6, 1954 e. B. ROLOSON LIGHTNING ARRESTER Filed March 5, 1952 if if /i' j fl' INVENTOR filerzmjflahaviz,

BY Gag ATTORNEYS I Patented July 6, 1954 UNITED STATES PATENT OFFICE LIGHTNING ARRESTER Glenn B. Roloson, Crestone, 0010. Application March 5, 1952, Serial No. 274,993

(Granted under Title 35, U. S. Code (1952),

sec. 266) 1 Claim.

A non-exclusive, irrevocable, royalty-fre e li cense in the invention herein described, for all governmental purposes, throughout the world, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States.

This application is a continuation of my prior co-pending application Serial No. 263,305 filed December 26, 1951, entitled Expulsion Type Lightning Arrester.

This invention relates to expulsion type lightning arresters and more particularly to ones where the arc is switched from a short direct ath to a long helical path after the initial impact of the surge causing the spark-over.

In the art of expulsion type lightning 'arresters the main objective is to have a short path for the initial spark-over. The initial are thus created ionizes the gases in the space between the electrodes, which space is usually bounded by fibre switches the path of the are from a short straight line path to a long helical path. One of the factors resulting in extinguishment of 'the arc is the great length of the helical path. Devices embodying this principle are shown and. described in my rior U. S. Patent 2,304,848 granted December 15, 1942, entitled Lightning Arrester, Gas Deflector Type, and in the article Spiral Arc Chokes Power Flow in New Arresters by Otto Ackermann and E. J. DeVal, A. I. E. E. Technical Paper 51189, published April 1951. My present invention is an improvement upon the devices described in the two references just mentioned, and has for its primary object to provide a longer and more efiective helical path (in relation to the length of the original spark-over path) than has been heretofore provided. 3

'In carrying out the foregoing object, I provide a smooth fibre rod extending inside of a tubular fibre member, with a small clearance space between the fibre rod and the inner wall of the tubular member. The inner wall of the tubular member defines a helical groove. The spark initially traverses the very narrow space between the rod and the inner wall of the tube but as soon as the arc causes the fibre to emit gases the latter switch the path of the arc to the long helical path.

While the material features of the combination claim appended hereto are recited in the claim themselves and while the scope of my invention is defined by the claim, it might be observed at this point in the specification that one of the features that distinguishes my present invention from the prior art is that concentric walls define walls, and causes the fibre to emit gases which a ringshaped space for the passage of the initial arc, the outer wall having a helical groove into which the arc is diverted after it becomes established. Since the helical groove is in the outer wall the groove is of great length, and moreover the switching operation is more effective and efficient than when the groove is located elsewhere.

In the drawings:

Figure 1 illustrates several of the components of my invention in a disassembled condition.

Figure 2 is a cross-sectional View of a lightning arrester embodying my present invention.

Referring to the drawings, the lightning arrester has a porcelain body H and a cylindrical metal element l2 surrounding the fibre tube l3. The metal end closure element 14 defines a ring of six vertical vent holes l5 and 16 disposed about the central axis of the apparatus. The closure element l4 supports a fibre rod l7. Metallic strap l8 extends beyond the outline of the insulator body H and serves as a ground as well as a support for the entire apparatus. Closure element 14 has an indent 2i} shaped to receive a complementary projection 28 at the lower end of fibre rod I1. The upper end of rod I! has a projection 22 shaped to fit into indent 23 in the upper metallic electrode 24. The outer wall of electrode 24 is threaded, is screwed into fibre tube l3, and is carried by bolt 25 which is in turn carried by washer 26 and nuts 21. A metallic gap element 28 forms one element of an external gap and element 29 forms the other element of the external gap. Helical groove 36 is formed on'the inside of fibre tube l3.

The rod 11 is held in place very accurately by the projections 2| and 22 which cooperate with indents 20 and 23 respectively. The axis of rod I1 is, therefore, very accurately aligned with that of fibre tube 13, and since the outer diameter of rod I1 is slightly smaller than the inner diameter of fibre tube l3 an air space on the order of a few hundredths of an inch (preferably not greater than one-tenth of an inch) exists around the wall of rod l1.

The gap element 29 may be connected to a power line carrying high voltage and capable of delivering heavy currents.

Operation Prior to the surge which causes spark-over there is an electric field between electrode 24 and metal shield I2 which to some degree ionizes the air adjacent electrode 24 in the space between rod l1 and tube 13.

When a large surge occurs a spark first passes vertically from electrode 24 along the side wall of rod I1 and substantially parallel to the axis thereof to the electrode l4 and thence to ground. The initial surge ionizes the gases in its path and allows an intense arc to follow, the power for the are being supplied by the high voltage power line which is of course connected to gap element 29) that is being protected by the lightning arrester. The intense heat of the arc causes fibre rod l I to emit gas, in the well known way, which gas switches the course of the are into the helical groove 35. This greatly lengthens the path of the arc and aids in its extinguishment. The fibre tube l3 may be made of gas evolving material, the same as the material for rod [1.

Since the lowermost end of groove 39 opens directly into annular passageway 3| which in turn opens into the ring of holes [5-16, it is clear that the lower end of groove 33 is efficiently vented to the atmosphere. This prevents explosive pressures from being built up inside of the lightning arrester.

I claim to have invented:

A lightning arrester comprising first and second electrodes, a smooth rod of gas-evolving malindrical member with a space between all parts of the inner surface of the cylindrical member and the outer surface of the rod greater than one-one hundredth of an inch and less than onetenth of an inch, the cylindrical member having a helical groove extending from one terminal to the other into which the are is switched by the evolved gases after the initial spark-over.

. References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,304,848 Roloson Dec. 15, 1942 2,591,370 Nelson et a1. Apr. 1, 1952 

